Apparatus and methods for maintaining a force upon tissue using a loop member

ABSTRACT

The present embodiments provide apparatus and methods for treating tissue by applying a force to the tissue. In one embodiment, the apparatus comprises a deployable segment having proximal and distal regions, a main body extending therebetween, and a loop member formed at the distal region of the deployable segment. A cannula having a bore is dimensioned to circumferentially surround at least a portion of the main body at a location proximal to the loop member, and a spring member is disposed between the cannula and the loop member. The proximal end of the spring member is affixed to the cannula, and the distal end of the spring member is movable to apply a compressive force to adjust the size of the opening of the loop member and compress tissue disposed within the opening of the loop member. In an alternative embodiment, the cannula is omitted, and a diameter of the loop member is configured to be reduced and increased any number of times before final deployment of the deployable segment.

The present patent document is a continuation application that claimsthe benefit of priority under 35 U.S.C. § 120 of U.S. patent applicationSer. No. 14/837,498, filed Aug. 27, 2015, which claims the benefit ofpriority under 35 U.S.C. § 120 of U.S. patent application Ser. No.12/913,469, filed Oct. 27, 2010 (now U.S. Pat. No. 9,144,428), whichclaims the benefit of the filing date under 35 U.S.C. § 119(e) ofProvisional U.S. Patent Application Ser. No. 61/256,430, filed Oct. 30,2009. All of the foregoing applications are hereby incorporated byreference in their entirety.

PRIORITY CLAIM

This invention claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 61/256,430, entitled “Apparatus and Methods forMaintaining a Force Upon Tissue Using a Loop Member,” filed Oct. 30,2009, the disclosure of which is hereby incorporated by reference in itsentirety.

BACKGROUND

The present embodiments relate generally to medical devices, and moreparticularly, to apparatus and methods for maintaining a force upontissue using a loop member.

There are various instances in which it may become necessary ordesirable to deliver a deployable snare into engagement with tissue. Forexample, such a snare may be used to induce hemostasis during apolypectomy, esophageal variceal bleeding, gastric variceal bleeding,and the excision of gastrointestinal stromal tumors. Further, deployablesnares may be useful in ligation of varices or polyps, closure ofgastrointestinal fistulas, and other procedures.

There are various commercially available deployable snares. Some of thedeployable snares comprise a loop made of nylon, one or more elongatedwires, sutures and/or other materials. The size and configuration of theloop may be adjusted using a stopper or cinching member that may besized to surround first and second ends of the loop. As the stopper orcinching member is distally advanced relative to the loop, the size ofthe loop may be decreased and a desired amount of force may be imposedupon target tissue.

While such snares are beneficial for providing an initial pressure uponthe target tissue, the diameter of the loop generally remains fixed inthe original configuration applied by the physician. In particular, thestopper or cinching member maintains the original diameter andconfiguration of the loop. It has been discovered by the applicantsthat, as tissue begins to necrose, the shape of the tissue originallyenclosed by the loop may change profile, and in particular, may decreasein size. Therefore, if the loop remains in its original fixedconfiguration, the loop may prematurely fall off of the tissue and failto maintain a continuous force upon the tissue over an extended periodof time.

SUMMARY

The present embodiments provide apparatus and methods for treatingtissue by maintaining a force upon the tissue using a loop member. Inone embodiment, the apparatus comprises a deployable segment havingproximal and distal regions and a main body extending therebetween. Aloop member is formed at the distal region of the deployable segment. Acannula having a bore is dimensioned to circumferentially surround atleast a portion of the main body at a location proximal to the loopmember, and a spring member is disposed between the cannula and the loopmember. The proximal end of the spring member is affixed to the cannula,and the distal end of the spring member is movable to apply acompressive force to adjust the size of the opening of the loop memberand compress tissue disposed within the opening of the loop member.

Advantageously, the provision of the spring member provides acompressive force to ensure that the loop member closely andcontinuously surrounds the target tissue. In particular, as the tissuenecroses or otherwise changes shape, the spring member causes the loopmember to assume a correspondingly reduced diameter. Therefore, unlikeother devices having a fixed diameter, the loop member will notprematurely lose its engagement with the target tissue over time.

The apparatus may be delivered using a catheter and stylet arrangement.In one example, a first retainer is disposed at the proximal region ofthe deployable segment, and a second retainer is disposed at a distalend of the stylet. Longitudinal movement of the stylet effectscorresponding longitudinal movement of the deployable segment when thefirst and second retainers are coupled together. The second retainer isconfigured to be coupled to the first retainer when a catheter ispositioned over both the first and second retainers, and further isconfigured to be disengaged from the first retainer when no longercovered by the catheter.

In an alternative embodiment, the cannula is omitted, and a diameter ofthe loop member is configured to be reduced and increased any number oftimes before final deployment of the deployable segment. Optionally, ineither embodiment, a sclerosing agent may be emitted from at least aportion of the loop member to achieve a desired biological effect.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be within the scope of the invention, and be encompassed bythe following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a side view of a first embodiment of an apparatus formaintaining a force upon tissue with a deployable segment and a deliverysegment in an unassembled state.

FIG. 2 is a side view of the apparatus of FIG. 1 in an assembled state.

FIG. 3A is a side sectional view depicting a cannula and a portion ofthe main body of the deployable segment of FIG. 1.

FIG. 3B is a side sectional view showing the first and second retainersof the apparatus of FIG. 1 in an assembled state.

FIGS. 4-7 are schematic views of exemplary method steps for using theapparatus of FIGS. 1-2 to maintain a force upon tissue.

FIG. 8 is a side view of an alternative embodiment of the loop member ofFIGS. 1-2.

FIG. 9 is a side view of a further alternative embodiment of the loopmember of FIGS. 1-2.

FIGS. 10-13 are side sectional views of exemplary method steps for usingan alternative apparatus to maintain a force upon tissue.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present application, the term “proximal” refers to a directionthat is generally towards a physician during a medical procedure, whilethe term “distal” refers to a direction that is generally towards atarget site within a patient's anatomy during a medical procedure.

Referring now to FIG. 1, a first embodiment of an apparatus 20 formaintaining a force upon tissue is shown. The apparatus 20 generallycomprises a deployable segment 30 and a delivery segment 70. As will beexplained in greater detail below, the deployable segment 30 may bedisengaged from the delivery segment 70 and remain engaged with tissueto provide a continuous compressive force upon the tissue.

The deployable segment 30 comprises proximal and distal regions 32 and34, respectively, and a main body 33 extending generally therebetween.The proximal region 32 comprises a first retainer 50, which may becoupled to the delivery segment 70 as explained further below. Thedistal region 34 comprises a loop member 35 having an opening 36 andfirst and second ends 37 and 38, as generally shown in FIG. 1. The loopmember 35 may be formed from one or more elongated wires or sutures,nylon, nitinol, stainless steel, and/or any combination of the aboveelements or other elements not specified.

The main body 33 of the deployable segment 30 extends proximally awayfrom the loop member 35. The main body 33 may comprise a portion of thefirst and second ends 37 and 38 of the loop member when the first andsecond ends 37 and 38 of the loop member 35 extend adjacent one anotherin a proximal direction towards the proximal region 32. In thisembodiment, a portion of the first and second ends 37 and 38 may be heatshrunk together, or otherwise coupled, a set distance from the loopmember 35 to form a substantially cylindrical segment spanning betweenthe proximal and distal regions 32 and 34.

In an alternative embodiment, the main body 33 may comprise a separatemember, i.e., distinct from the first and second ends 37 and 38 of theloop member 35. For example, the main body 33 may comprise a length ofwire that is coupled to the first and second ends 37 and 38 of the loopmember 35 and extends proximally therefrom. The coupling may be achievedusing an adhesive, solder, weld, heat shrink tubing, mechanicalcoupling, or any other suitable means.

Referring still to FIG. 1, the deployable segment 30 further comprises aspring member 40 having a proximal end 42, a distal end 44, and aplurality of turns 41 disposed therebetween. The spring member 40circumferentially surrounds at least a portion of the main body 33 andthe first and second ends 37 and 38 of the loop member 35. Spring member40 may comprise a compression spring, as shown in the embodimentsherein, and may be formed of metal, plastic or another suitablematerial. Spring member 40 may comprise a variable or constant forcespring. Alternatively, spring member 40 may comprise a resilientcompressive member that optionally comprises a plurality of turns. Inthe latter example, the spring member may comprise a solid elastomericcomponent that may be compressed and impose the compressive forcesdescribed herein.

The spring member 40 may comprise a material, shape and configurationthat may be tailored based on a given application. In particular, thediameter, wire thickness, stiffness and/or other features of the springmember 40 may be varied as needed for a particular procedure to meetanatomical constraints and/or vary the force imposed on tissue segments.For example, a substantially stiff spring member 40 may provide anincreased force upon the loop member 35 to reduce the likelihood of thedeployable segment 30 becoming disengaged from tissue after deployment,as explained further in FIGS. 4-7 below.

In the embodiment of FIGS. 1-2, the spring member 40 is disposed betweena cannula 45 and the loop member 35. The proximal end 42 of the springmember 40 may be secured to the cannula 45 using an adhesive, solder,weld, mechanical attachment device, or any other suitable mechanism. Themain body 33 of the deployable segment 30 extends through a bore 46 ofthe cannula 45, as best seen in FIGS. 1 and 3A.

In one embodiment, a one-way mechanism is employed wherein the main body33 of the deployable segment 30 may be advanced in a proximal directionthrough the cannula 45 with a predetermined pulling force provided by aphysician, but the main body 33 cannot be advanced in a distal directionthrough the cannula 45. As such, the cannula 45 serves as a “stop” forretaining the spring member 40, as explained greater with reference toFIG. 5 below.

An interior region of the bore 46 of the cannula 45 and an exteriorportion of the main body 33 may comprise a one-way interlockingmechanism to ensure movement of the main body 33 in a proximal directiononly through the cannula 45, or a frictional fit may be employed suchthat the main body 33 bunches up on a proximal side of the cannula 45 toinhibit distal advancement. For example, in one embodiment depicted inFIG. 3A, teeth 49 may be angled in a proximally direction into the bore46 of the cannula 45 for causing one-way movement of the main body 33relative to the cannula 45. The spring member 40 is thus maintainedbetween the cannula 45 and the loop member 35, and likewise can becompressed therebetween to exert a force on the loop member 35. Notably,the cannula 45 may comprise a relatively smaller length collar-likestructure, as depicted herein, or may comprise an increased, elongatedlength.

The delivery segment 70 generally comprises inner and outer catheters 80and 90, respectively, each having proximal and distal ends and lumensextending therebetween. The inner catheter 80 is configured to bedisposed within the lumen of the outer catheter 90, as generallydepicted in FIG. 1. A distal region of the inner catheter 80 may becoupled to, or formed integrally with, a reinforcement cannula 84. Thereinforcement cannula 84 of the inner catheter 80 may abut the cannula45 disposed over the main body 33, as depicted in FIG. 2 and explainedfurther below.

The delivery segment 70 further comprises a stylet 75, which has anouter diameter configured for movement within the lumen of the innercatheter 80. In one embodiment, the stylet 75 and the main body 33comprise generally identical outer diameters, such that both componentsmay be advanced within the lumen of the inner catheter 80 when coupledtogether.

In order to deliver the deployable segment 30 to a target tissue siteusing the delivery segment 70, the first retainer 50 of the deployablesegment 30 is joined to a second retainer 60 of the delivery segment 70.The second retainer 60 may be formed integral with or coupled to adistal region of the stylet 75.

The stylet 75 extends proximally and may be coupled to a handle that maybe manipulated by a physician. In use, the first retainer 50 is joinedto the second retainer 60, as explained greater below, and longitudinalmovement of the stylet 75 affects sizing of the loop member 35. When adesired sizing of the loop member 35 is achieved, the first retainer 50is configured to be disengaged from the second retainer 60, leaving onlythe deployable segment 30 inside the body, as explained in FIGS. 6-7below.

Various types of complementary first and second retainers 50 and 60 maybe used to facilitate controlled release of the deployable segment 30 inaccordance with the present embodiments. Suitable complementary firstand second retainers 50 and 60 are described in commonly-assigned U.S.patent application Ser. No. 11/807,827, filed May 30, 2007 (hereinafter“the '827 application”), which is hereby incorporated by reference inits entirety. The first and second retainers 50 and 60 shown in thepresent application therefore are one of multiple possible types ofretaining mechanisms for controlled release of the deployable segment30.

In the embodiment herein, the second retainer 60 is complementary to thefirst retainer 50 so that the first and second retainers 50 and 60 canbe matingly joined. The first retainer 50 has a knob 55 disposedproximal to a notch 56, as shown in FIG. 3B. In a symmetrical manner,the second retainer 60 has a knob 65 disposed distal to a notch 66, asshown in FIG. 3B. The knobs 55 and 65 may approximate the shape of ahalf-cylinder having a flat surface, as depicted in FIG. 3B, oralternatively may comprises a rounded configuration, as describedfurther in the '827 application.

The first and second retainers 50 and 60 are joined with each other bylocating the knob 55 of the first retainer 50 within the notch 66 of thesecond retainer 60, and by locating the knob 65 of the second retainer60 within the notch 56 of the first retainer 50. When joined, the firstand second retainers 50 and 60 form a substantially continuous cylindershape having substantially the same outer diameter, as shown in FIG. 3B.The outer diameter of the first and second retainers 50 and 60, whenmated, preferably is slightly less than an inner diameter of the innercatheter 80, and further preferably is substantially identical to theouter diameter of the main body 33, as depicted in FIG. 3B.

It should be noted that although the first retainer 50 matingly joinswith second retainer 60, they will not retain a joined position unlessthey are held together. Since the inner catheter 80 comprises an innerdiameter that is slightly larger than the mated first and secondretainers 50 and 60, the inner catheter 80 therefore holds and maintainsthe first and second retainers 50 and 60 in a mating position, as longas the inner catheter 80 covers both the mating first and secondretainers 50 and 60, as shown in FIG. 3B.

Referring now to FIGS. 4-7, an exemplary use of the apparatus 20 isdescribed. In a first step, the deployable segment 30 may be coupled tothe delivery segment 70 outside of the patient's body. The stylet 75 maybe loaded into the inner catheter 80 such that the second retainer 60extends just distal to the reinforcement cannula 84 of the innercatheter 80. The first retainer 50 of the deployable segment 30 ismatingly joined with the second retainer 60, as described above. Themating first and second retainers 50 and 60 then are loaded into theinner catheter 80 and advanced in a proximal direction. The deployablesegment 30 may be advanced proximally into the inner catheter 80 untilthe cannula 45 over the main body 33 is adjacent to the reinforcementcannula 84 at the distal end of the inner catheter 80, as depicted inFIG. 4. At this time, the loop member 35 may be provided in a relativelyopen diameter configuration and disposed distal to the spring member 40.The spring member 40 is in a relaxed state having a length L₁, as shownin FIG. 4.

In this state, the outer catheter 90 may be advanced distally over allof the components to enclose the loop member 35. An endoscope may bedelivered through patient's anatomy and disposed proximal to targettissue T. The outer catheter 90, with components loaded therein, thenmay be advanced through a lumen of the endoscope until a distal regionof the outer catheter 90 is positioned distal to the endoscope. At thistime, the outer catheter 90 may be retracted proximally, relative to theother components, to expose the loop member 35 and distal end of theinner catheter 80, as shown in FIG. 4. The loop member 35 then may bepositioned around the target tissue T, under direct endoscopicvisualization, and/or using other visualization techniques.

Referring to FIG. 5, in a next step, the size of the loop member 35 maybe reduced to apply a compressive force around the target tissue T. Inparticular, the stylet 75 is retracted in a proximal direction relativeto the catheter 80. Since the second retainer 60 of the stylet 75 isengaged with the first retainer 50 of the deployable segment 30 insideof the inner catheter 80, the deployable segment 30 is also retracted ina proximal direction. At this time, the main body 33 of the deployablesegment 30 is moved in a proximal direction through the cannula 45, asdepicted in FIG. 3A and FIG. 5. As the cannula 45 becomes positionedmore distally along the main body 33, the loop member is positioned moreproximally relative to the cannula 45 and the spring member 40compresses.

The inner catheter 80 may be held steady during the retraction of thestylet 75. As the main body 33 and loop member 35 are retracted via thestylet 75, the cannula 45 abuts the reinforcement cannula 84 and cannotbe further retracted, thereby limiting the amount of compression of thespring member 40. In effect, the loop member 35 is tightened around thetarget tissue T while the main body 33 and/or first and seconds ends 37and 38 are pulled through the stationary cannula 45.

Upon retraction, the loop member 35 compresses the spring member 40 fromthe relaxed length L₁ to a compressed length L₂. In particular, thedistal end 44 of the spring member 40 is urged proximally by the loopmember 35 and/or the tissue T, while the proximal end 42 of the springmember 40 is held stationary by the cannula 40 abutting against thereinforcement cannula 84 of the inner catheter 80.

As noted above, a one-way arrangement may be employed wherein the mainbody 33 may be advanced only in a proximal direction through the cannula45, e.g., using a friction fit and/or one-way mechanism. Therefore, whenthe loop member 35 is tightened around the target tissue T, the mainbody 33 cannot slide distally relative to the cannula 45 toinadvertently increase the diameter of the loop member 35. At this time,the loop member 35 is tightened around the target tissue T, and thespring member 40 is compressed and pushes in a distal direction againstthe loop member 35 to promote closure of the loop member 35 around thetarget tissue T.

Referring now to FIG. 6, when the loop member 35 is tightened around thetarget tissue T, the physician may distally advance the stylet 75relative to inner catheter 80 to expose the junction between the firstand second retainers 50 and 60, thereby detaching the retainers andleaving the deployable segment 30 coupled to the target tissue T.Alternatively, the physician may proximally retract the inner catheter80 relative to the stylet 75 to expose the retainer junction. Oncedetached, the inner and outer catheters 80 and 90, along with the stylet75, are removed from the patient.

Referring now to FIG. 7, the target tissue T has necrosed over anelapsed period of time. As this happens, the size of the target tissue Thas decreased. Advantageously, the provision of the spring member 40provides a continuous compressive force to ensure that the loop member35 may be continuously tightened around the target tissue T. Inparticular, as the tissue necroses, the spring member 40 causes the loopmember 35 to assume a correspondingly reduced diameter. Therefore,unlike other devices having a fixed loop diameter, the loop member 35will not prematurely lose its engagement with the target tissue T as thetissue necroses or otherwise changes shape. Once the target tissue T hasbeen sufficiently treated, then the deployable segment 30 may lose itsengagement and pass through the body naturally.

Referring now to FIG. 8, in an alternative embodiment, a deployablesegment 30′ is similar to the deployable segment 30 described above,with a main exception that the deployable segment 30′ comprises aplurality of barbs 95 that anchor into the tissue T. The provision ofthe barbs 95 may reduce the likelihood of a loop member 35′ slipping offthe tissue T while tension is applied to decrease the diameter of theloop member around the tissue. The barbs may be formed integrally withthe loop member 35′, or attached thereto using soldering or othertechniques. Preferably, the barbs are oriented at an angle such thatthey may be retracted through the spring member 40 with relative ease,as depicted in FIG. 8.

Referring now to FIG. 9, in a further alternative embodiment, adeployable segment 30″ is similar to the deployable segment 30 describedabove, with a main exception that the loop member 35″ is configured toprovide sclerotherapy to promote scar formation, facilitate hemostasis,or perform another desired function. In one example, a sclerosing agentmay be delivered through outlet bores 97 formed in an outer surface of aloop member 35″. The sclerosing agent may be injected into the bores 97,or the loop member 35″ may comprise a lumen therein that houses thesclerosing agent for dispersal through the bores 97. Alternatively, oneor more sclerosing agents may be coated onto an outer surface of theloop member 35″ for elution into the tissue. While numerous suitablesclerosing agents may be used in conjunction with the loop member 35″,one exemplary agent comprises hydroxypolyethoxydodecan.

In a further alternative embodiment, the inner catheter 80 may comprisea torquing member, such as a torque cable, coupled to a portion of thedeployable segment 30 to enable rotation of the loop member 35, therebyfacilitating orientation and placement of the loop member 35 aroundtarget tissue. In this example, the inner catheter 80 may comprise atorque cable to enable rotation of the loop member 35, or another cablemay be coupled directly to the deployable segment 30.

Referring now to FIGS. 10-13, in an alternative embodiment, apparatus120 having loop member 135 is provided for maintaining a force upontissue. The apparatus 120 generally comprises a deployable segment 130,a stylet 165, a plug member 175, and an outer catheter 180 having adetachable end region 190.

The deployable segment 130 of the apparatus 120 preferably is similar tothe deployable segment 30 described above, with a main exception thatcannula 45 has been omitted. Moreover, a proximal region 132 of thedeployable segment 130 comprises a first retainer 150 in the form of ahook, which may engage and disengage from a second retainer 160 in theform of a loop extending from the stylet 165, as explained greaterbelow. The deployable segment 130 further comprises a main body 133, adistal region 134, and the loop member 135 having an opening 136therein, as shown in FIG. 10.

In the embodiment of FIGS. 10-13, the outer catheter 180 comprises alumen 182 that is sized to receive multiple components. In addition tothe stylet 165 coupled to the deployable segment 130, the lumen 182 issized to receive a stylet 173 that is detachably coupled to the plugmember 175. The stylet 173 and the plug member 175 may be disposedadjacent to the stylet 165 within the lumen 182, as depicted in FIG. 10.

The detachable end region 190 comprises proximal and distal segments 192and 194, respectively, and lumen 195 formed therein. The proximal anddistal segments 192 and 194 may form a continuous inner surface,however, the proximal segment 192 has a stepped-down outer diametercompared to the distal segment 194, as shown in FIG. 10. A distal region182 of the outer catheter 180 may be frictionally coupled around theproximal segment 192 of the detachable end region 190, thereby providinga substantially flush outer diameter as depicted in FIG. 10.

A spring member 140 may be coupled to the distal segment 194 of thedetachable end region 190, and extend distally therefrom, as shown inFIG. 10. In this embodiment, the spring member 140 is optionallytapered, such that a larger proximal diameter is attached to thedetachable end region 190 and encircles the lumen 195, while a smallerdistal diameter is only slightly larger than the main body 133 of thedeployable segment 130, as shown in FIG. 10.

In use, the apparatus 120 is delivered towards a target tissue site asgenerally described above. In particular, a catheter may be used tocover the loop member 135, and the components may be delivery through alumen of an endoscope. For illustrative purposes, the target tissue isnot shown in the embodiments of FIGS. 10-13, but engagement of the loopmember 135 with the target tissue would be similar to that shown inFIGS. 4-7 above.

In a first step, the loop member 135 may be positioned around the targettissue, under direct endoscopic visualization and/or using othervisualization techniques, as generally described above. In a next step,depicted in FIG. 11, the size of the loop member 135 may be reduced toapply a compressive force around the target tissue. In particular, thestylet 165 is retracted in a proximal direction. Since the secondretainer 160 of the stylet 165 is engaged with the first retainer 150 ofthe deployable segment 130, the deployable segment 130 is also retractedin a proximal direction. At this time, the main body 133 of thedeployable segment is moved in a proximal direction through the springmember 140, as depicted in FIG. 11.

Preferably, the outer catheter 180 is held steady during the retractionof the stylet 165 and the loop member 130. Accordingly, the loop member135 is tightened around the target tissue, and the main body 133 and/orfirst and seconds ends 137 and 138 are pulled through the spring member140. Upon retraction, the loop member 135 compresses the spring member140 from the relaxed length shown in FIG. 10 to the compressed lengthshown in FIG. 11.

Advantageously, in this embodiment, a physician may increase and reducethe initial diameter of the loop member 135 around the tissue as manytimes as desired. For example, after the stylet 165 has been retractedto reduce the diameter of the loop member 135 as shown in FIG. 11, ifthe sizing is not desirable then the physician may simply distallyadvance the stylet 165 to cause distal advancement of the loop member135 to increase the size of the loop member 135. This sequence ofadvancement and retraction of the stylet 165, and corresponding changesto the size of the loop member 135, may be performed as needed duringinitial sizing of the loop member 135 around the tissue.

Referring to FIG. 12, when a desired sizing of the loop member 135around the tissue has been achieved, the stylet 173 coupled to thedetachable plug member 175 is distally advanced within the lumen 182 ofthe outer catheter 180. The stylet 173 is advanced until a distal region177 of the detachable plug member 175 is wedged adjacent to the mainbody 133 of the deployable segment 130 within the lumen 195 of thedetachable end region 190, as shown in FIG. 12. In this embodiment, thedetachable plug member 175 may comprise an elastomeric or other suitablematerial having a proximal bore 178 that is sized to engage a distal endof the stylet 173 using a friction fit. The distal region 177 maycomprise a tapered end to facilitate distal advancement within the lumen182 of the outer catheter 180, and subsequently into the lumen 195 ofthe detachable end region 190, as depicted in FIG. 12. Moreover, radialprotrusions 179 may be provided on the detachable plug member 175 topromote a secure engagement between the main body 133, the detachableplug member 175, and the detachable end region 190. In the state shownin FIG. 12, the positioning of the main body 133 and loop member 135 arefixed relative to the compressed spring member 140.

In a next step, a physician may proximally retract the outer catheter180 relative to the stylet 165 to expose the junction between the firstand second retainers 150 and 160, thereby detaching the retainers.Further, proximal retraction of the outer catheter 180 relative to thedetachable end region 190, beyond a predetermined frictional forcethreshold, will cause detachment of the detachable end region 190 fromthe outer catheter 180. Similarly, proximal retraction of the stylet173, beyond a predetermined frictional force threshold, will causedetachment of the plug member 175 from the stylet 173. Once detached,the outer catheter 180, along with the stylets 165 and 173, are removedfrom the patient, leaving the deployable segment 130 coupled to thetarget tissue, as shown in FIG. 13. The plug member 175 and detachableend region 190 remain engaged with the deployable segment 130.

As noted above, the target tissue within the loop member 135 willnecrose over an elapsed period of time. As this happens, the size of thetarget tissue may decrease. Advantageously, the provision of the springmember 140 provides a continuous compressive force to ensure that theloop member may continuously surround the target tissue. In particular,as the tissue necroses, the spring member 140 causes the loop member 135to assume a correspondingly reduced diameter, such that the loop member135 will not prematurely lose its engagement with the target tissue asthe tissue necroses or otherwise changes its shape. Once the targettissue has been sufficiently treated, e.g., reduced to a significantlyreduced size, then the deployable segment 130, the plug member 175 andthe detachable end region 190 may pass through the body naturally.

In further alternative embodiments, the spring members 40 and 140described above may be omitted, and the loop members 35 and 135 maycomprise materials that are sensitive to pH, temperature and/or light.In such embodiments, the user may place the loop member around thetarget tissue with a desired initial amount of tension, as describedabove. When the loop member is introduced to the pH or temperature ofthe gastric system or other bodily conduit, or exposed to light from anendoscope, the diameter of the loop member may decrease to maintainfurther compression upon the target tissue. Suitable pH sensitivematerials comprise chitosan and polyacrylic acid, while a suitabletemperature sensitive material comprises polyolefin, and a suitablelight sensitive material comprises Azobenzene-based photodevices. Instill further alternative embodiments, the loop member may comprise abiodegradeable material that is configured to degrade after a suitableforce has been applied to the target tissue over a desired period oftime.

In an alternative method, the apparatuses 20 and 120 described above maybe used for substantially full-thickness excision of tissue, includinggastrointestinal stromal tumors (GIST). In this method, a tissueretractor may be used to pull the entire GIST into the loop member 35 or135. The loop member 35 or 135 then may be deployed, as explained above,to strangulate blood supply to the GIST, resulting in necrosis andsloughing. Scar formation at the looping site prevents perforation ofthe tissue wall. Such a method is an improvement that may yield fewercomplications relative to current techniques involving excision of thetissue and subsequent attempts to close the perforation in a secondstep.

In yet a further alternative method, the loop member 35 described hereinmay be used to close defects, such as perforations, within thegastrointestinal tract. In this example, the loop member 35 may be usedin conjunction with a tissue retraction member to bunch tissuesurrounding the defect together before deployment of the loop member 35.For example, the tissue retraction member may comprise a balloon ortacking device that is disposed through the opening and used to form apolyp-like section of tissue surrounding the opening, as generallydescribed in U.S. Patent Application Ser. No. 61/256,619 (“the '619application”), filed Oct. 30, 2009, which is hereby incorporated byreference in its entirety. The tissue retraction member may be advancedin a distal direction through the bodily opening with the tissueretraction member in a contracted state, then is actuated from thecontracted state to an expanded state at a location distal to theopening, as explained in the '619 application. Then, the tissueretraction member may be proximally retracted to engage first and secondserosal tissue regions at least partially surrounding the opening,thereby causing the first and second serosal regions to be disposed inan adjacent relationship in a polyp-like manner. At this time, the loopmember 35 of the present embodiments may be placed around the first andsecond serosal tissue regions and deployed to apply and maintain acompressive force, as generally explained above, thereby holding thetissue regions together to close the opening.

As an alternative to using a balloon or tacking device as the tissueretraction member, a T-shaped anchor may be placed through the defect.In this embodiment, after the T-shaped anchor is placed through thedefect, sutures coupled to the T-shaped anchor may be retracted to causethe first and second serosal regions to be disposed in an adjacentrelationship in a polyp-like manner. Subsequently, the loop member 35may be advanced over the sutures and tightened around the adjacenttissue segments to hold them together. Alternatively, two or moredifferent T-shaped anchors may be placed through tissue surrounding thedefect, then retracted proximally to create a polyp-like bundle that theloop member 35 may be placed over.

While various embodiments of the invention have been described, theinvention is not to be restricted except in light of the attached claimsand their equivalents. Moreover, the advantages described herein are notnecessarily the only advantages of the invention and it is notnecessarily expected that every embodiment of the invention will achieveall of the advantages described.

We claim:
 1. Apparatus for treating tissue by applying a force to thetissue, the apparatus comprising: a deployable segment having proximaland distal regions, and a main body extending therebetween; a loopmember formed at the distal region of the deployable segment, the loopmember defining an opening that is adjustable in size; and a deliverysegment that can be disengaged from the deployable segment, wherein theloop member is adjustable while the deployable segment is disengagedfrom the delivery segment.
 2. The apparatus of claim 1, wherein thedeployable segment comprises a first retainer and the delivery segmentcomprises a second retainer, wherein the first retainer and the secondretainer are coupled during a delivery state, and wherein the firstretainer and the second retainer are uncoupled when the deployablesegment is disengaged from the delivery segment.
 3. The apparatus ofclaim 2, wherein the first retainer and the second retainer are heldtogether in a coupled state when surrounded by a catheter disposed overa junction at which the first and second retainers engage one another.4. The apparatus of claim 2, wherein the second retainer is disposed ata distal end of a stylet.
 5. The apparatus of claim 4, wherein thestylet and the main body of the loop member comprise substantiallyidentical outer diameters.
 6. The apparatus of claim 1 furthercomprising: a cannula having a bore extending therethrough, wherein thecannula is dimensioned to circumferentially surround at least a portionof the main body at a location proximal to the loop member; and anadvanceable segment disposed between the cannula and the loop member,the advanceable segment having proximal and distal ends, and dimensionedto circumferentially surround at least a portion of the main body,wherein the proximal end of the advanceable segment is coupled to thecannula, and wherein the distal end of the advanceable segment ismovable to apply a compressive force to adjust the size of the openingof the loop member and compress tissue disposed within the opening ofthe loop member.
 7. The apparatus of claim 6 wherein the proximal end ofthe advanceable segment is secured to the cannula in a fixedrelationship.
 8. The apparatus of claim 6 wherein the advanceablesegment comprises a spring member.
 9. The apparatus of claim 8 whereinthe loop member causes compression of the spring member when the mainbody is retracted in a proximal direction through the cannula.
 10. Theapparatus of claim 6 wherein the cannula frictionally engages the mainbody of the loop member.
 11. The apparatus of claim 10 wherein theadvanceable segment comprises a spring member that does not havesufficient force to overcome the friction between the cannula and themain body.
 12. The apparatus of claim 10 wherein the main body of thedeployable segment is configured for longitudinal movement only in aproximal direction through the cannula.
 13. Apparatus for treatingtissue by applying a force to the tissue, the apparatus comprising: adeployable segment having proximal and distal regions, and a main bodyextending therebetween; a loop member formed at the distal region of thedeployable segment, the loop member defining an opening that isadjustable in size; a delivery segment that can be disengaged from thedeployable segment, wherein the loop member comprises a first diameterwhen the deployable segment is disengaged from the delivery segment, andwherein the loop member comprises a second diameter when the deployablesegment remains disengaged from the delivery segment, wherein the seconddiameter is less than the first diameter.
 14. The apparatus of claim 13,wherein the deployable segment comprises a first retainer and thedelivery segment comprises a second retainer, wherein the first retainerand the second retainer are coupled during a delivery state, and whereinthe first retainer and the second retainer are uncoupled when thedeployable segment is disengaged from the delivery segment.
 15. Theapparatus of claim 13 further comprising: a cannula having a boreextending therethrough, wherein the cannula is dimensioned tocircumferentially surround at least a portion of the main body at alocation proximal to the loop member; and an advanceable segmentdisposed between the cannula and the loop member, the advanceablesegment having proximal and distal ends, and dimensioned tocircumferentially surround at least a portion of the main body, whereinthe proximal end of the advanceable segment is coupled to the cannula,and wherein the distal end of the advanceable segment is movable toapply a compressive force to adjust the size of the opening of the loopmember and compress tissue disposed within the opening of the loopmember.